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Thread: 502 Timing

  1. #1
    My Boats:
    Fountain 1992 35 Lightning
    Join Date
    Oct 2000
    Overland Park, KS USA

    502 Timing

    I have seen a lot of talk back and forth on timing for full advance, also saw this in Dennis Moores book. But why does Merc put such a small advance box on the older 502 mags with carbs?? What should be the full advanced timing? If you bump the timing say to 12 initial do you need to run premium fuel?

  2. #2
    VIP Member VIP Member JaayTeee's Avatar
    My Boats:
    2002 baja 33 o/l 575sci's
    Join Date
    Nov 2002
    My thoughts on this is,
    back when these engines/ drives
    came out, they would only offer them
    with 1:36 gear ratio's to prevent
    drive issues.
    Retarded timing= less low end torque,
    easier on the drive, when coming out of the

    As I recall the module only has 20* of advance
    built in, that gives you a total of 28* full,

    I had a 24' boat with the engine mentioned,
    it was relatively light 3600#'s, but it was a pig
    out of the hole
    I set my advance up to 14* initial, giving my
    34* total, made a big difference on acceleration.
    I didn't run premium either, I didn't notice any
    detonation, I ran this for 5 years,no problem.

    hope this helps.

  3. #3
    My Boats:
    Fountain 1992 35 Lightning
    Join Date
    Oct 2000
    Overland Park, KS USA


    I had not thought of it that way. Although I have 1:50 drives. My hole shot is pretty good actually and the boat stays on plane at low RPM. I have bumped my timing a little (last season), but was starting to think about the upcoming season and stuff to put on my to do list. It seems to me that there is more power available there with some better tuning. I appreciate your feedback. Any other input out there? Thanks!!

  4. #4
    Charter Member # 55 Charter Member Griff's Avatar
    My Boats:
    ..........32........... Active Thunder
    Join Date
    Oct 2000
    Your module should have the amount of advance stamped into the case as part of the part#. It is probably a 24* degree advance. Whatever it is, set the timing to 34* at full advance. This will come in at 3000-3800 depending on which module you have. Factory setting is 32*.

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